In the field of firearms, auto-loading firearms, which include semi-automatic and automatic rifles, often include a bolt carrier reciprocally moveable within an upper receiver, which moves a bolt of the firearm through a firing cycle. Many of these firearms employ a rotary bolt having lugs which is rotated to engage and disengage the lugs with a breech. During movement of the bolt carrier through the firing cycle, a cam pin, carried by the bolt, moves in a helical cam track formed in the bolt carrier. Movement of the cam pin in the cam track rotates the bolt to lock and unlock the lugs to the breech. The bolt carrier is moved within the upper receiver by various mechanisms such as gas or mechanical operating systems. The operating system moves a bolt carrier rearwardly from a forward firing position in which the bolt is in a locked position, to a rearward position. During the rearward movement, the bolt is unlocked from the breech and any casing is removed during the rearward movement. A buffer/action spring, typically a compression spring, moves the bolt carrier forwardly. During the forward movement, the bolt strips a cartridge from a magazine and pushes the cartridge into the firing chamber located at the breech end of the barrel. The lugs of the rotary bolt are moved to the locked position ready to fire. Apart from the rotary motion, the cam pin also moves along tracks formed in the upper receiver during forward and rearward movement of the bolt carrier. While the cam pin works effectively, the edges of the cam pin riding against portions of the upper receiver can cause scoring, and may inhibit the movement of the bolt carrier during the firing cycle.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.